文件读取与异常
1、文件读取和写入
shell 主要利用管道命令读取和写入文件，python主要是利用open函数，write函数完成
import os
data=open(finename)
print(data.readline());
data.close()
通过open打开文件，得到文件对象，通过for循环输出每行，如下代码所示：
[nxuser@PSjamsBond-0-0-0 ~]$ vi readfile.py
#!/bin/python
import os
data=open("readme.txt")
for line in data:
print(line)
data.close()
输出如下：为什么间隔那么大？？？
[nxuser@PSjamsBond-0-0-0 ~]$ python readfile.py
aaa
bbb
ccc
ddddddddd
Shell读取文件如下，利用管道命令作为输入：
[nxuser@PSjamsBond-0-0-0 ~]$ vi readfile.sh #!/bin/bash cat readme.txt| while read line do echo $line done [nxuser@PSjamsBond-0-0-0 ~]$ ./readfile.sh aaa bbb ccc ddddddddd
python读取文件后，可以获取文件的更多信息，如名称，扩展名， 访问模式等：
[nxuser@PSjamsBond-0-0-0 ~]$ vi readfile.py
#!/bin/python
import os
filename=raw_input("please input filename:");
print(filename)
#access mode , is buffer
fo=open(filename,"r")
for line in fo:
print(line)
#
print("the file name is: "),fo.name
print("the file mode is:"),fo.mode
fo.close()
python写入文件，利用write函数，但是文件的模式应该为可写入的，比如r+,w+,wb等
#!/bin/python
import os
filename=raw_input("please input filename:");
print"the input file name is",(filename)
#access mode , is buffer
fo=open(filename,"r+")
for line in fo:
print(line)
#
print("the file name is: "),fo.name
print("the file mode is:"),fo.mode
# write file
fo.write("python is greate!!!")
fo.close()
shell写入文件通过管道命令实现:
通过两个管道命令就可以实现：
1. > 符号表示将信息写入文件中
2. >> 符号表示在已有的文件中添加信息
#!/bin/bash read -p "please input file name:" filename cat $filename| while read line do echo $line done echo "shell is powerful" >>$filename
read函数读取指定字节数，不指定读取全部，此函数注意指针的位置，如果循环输出后进行读取，内容肯定为空，因为指针位于文件末尾，此时需要从头开始，利用seek函数，可以利用tell查询指针位置
#!/bin/python
import os
filename=raw_input("please input filename:");
print"the input file name is",(filename)
#access mode , is buffer
fo=open(filename,"r+")
for line in fo:
print(line)
#
print("the file name is: "),fo.name
print("the file mode is:"),fo.mode
# write file
#fo.write("python is greate!!!")
#read function
# the position is at the end of file, so the read result is empty
# Need to reset the position to zero
str=fo.read(20)
print("the result of read function is :"),str,fo.tell()
fo.seek(0,0)
print("the result of read function is :"),str,fo.tell()
str=fo.read(20)
print("the result of read function is :"),str,fo.tell()
fo.close()
输出如下
[nxuser@PSjamsBond-0-0-0 ~]$ python readfile.py please input filename:readme.txt the input file name is readme.txt aaa bbb ccc ddddddddd python is greate!!!shell is powerful python is greate!!!python is greate!!! the file name is: readme.txt the file mode is: r+ the result of read function is : 97 the result of read function is : 0 the result of read function is : aaa bbb ccc dddddddd 20
2. 文件及目录操作
通过os模块实现文件重命名，删除，目录等操作，新建由open函数完成。
[nxuser@PSjamsBond-0-0-0 ~]$ vi fileanddirectory.py
#!/bin/python
import os
fo=open("testfile.txt","w+")
os.rename("testfile.txt","newtestfile.txt")
os.remove("newtestfile.txt")
#os.mkdir("kerry")
os.chdir("/home/nxuser")
print "the current director is:", os.getcwd()
是否存在判断
os.path.isfile()
os.path.exists()
#!/bin/python
import os
fo=open("testfile.txt","w+")
isExist=os.path.isfile("testfile.txt")
print("the vaule of isExist is :"),isExist
os.rename("testfile.txt","newtestfile.txt")
os.remove("newtestfile.txt")
try:
os.mkdir("kerry")
except OSError:
pass
dirExist=os.path.exists("./kerry")
print("the value of dirExist is:"),dirExist
os.chdir("/home/nxuser")
print "the current director is:", os.getcwd()
File 对象方法: file对象提供了操作文件的一系列方法。
OS 对象方法: 提供了处理文件及目录的一系列方法。
3. 键盘输入
shell键盘输入利用read， -p参数指定提示语，
read -p "please input" filename
[nxuser@PSjamsBond-0-0-0 ~]$ vi readfile.sh #!/bin/bash read -p "please input file name:" filename cat $filename| while read line do echo $line done
python利用raw_input 和input函数
[nxuser@PSjamsBond-0-0-0 ~]$ vi readfile.py
#!/bin/python
import os
filename=raw_input("please input filename:");
print(filename)
data=open(filename)
for line in data:
print(line)
data.close()
此处利用input报错，不知为何？？？？
使用input和raw_input都可以读取控制台的输入，input()只能接受int,float或由它们组成的表达式，并且返回运算结果
详见此文：http://blog.csdn.net/wusuopubupt/article/details/23680491
4. 异常管理
try:
你的代码逻辑
except:
异常处理逻辑
try:
你的代码逻辑
except IOError:
异常处理逻辑
#!/bin/python
import os
filename=raw_input("please input filename:");
print"the input file name is",(filename)
#access mode , is buffer
try:
fo=open(filename,"r+")
except IOError:
print("can not find file")
else:
print("this is in else ")
finally:
print("this is in finally ")
raise TypeError("my type error")
输出如下：
[nxuser@PSjamsBond-0-0-0 ~]$ python readfile.py
please input filename:aaa
the input file name is aaa
can not find file
this is in finally
Traceback (most recent call last):
File "readfile.py", line 18, in <module>
raise TypeError("my type error")
TypeError: my type error
shell中除了退出码判断执行情况外，利用trap命令捕获异常，此处不详细介绍